Influence of thickness and dielectric properties on implantation efficacy in plasma immersion ion implantation of insulators

Plasma immersion ion implantation of insulators is an interesting topic both theoretically and industrially. The net energy of the incident ions is dictated by the surface potential and for conductors is equal to the voltage applied to the backside or sample stage. However, the poor electrical conductivity of insulating materials can lead not only to charging during ion bombardment but also reduced surface potential due to the capacitance effect. In the work described in this paper, we theoretically and experimentally investigate the influence of the thickness and dielectric properties of insulating materials on the implantation efficacy. The use of mesh-assisted PIII by covering the insulating materials with an electrically conducting cage to enhance the implantation efficacy is also compared experimentally. Our theoretical results suggest that a low plasma density induces less surface charges and higher surface potential. Our experimental data show good agreement with the theoretical results and mesh-assisted PIII does yield net improvement.